At the Height of Summer (PG)

In the realm of the sensuous

Several moments in At the Height of Summer, the new film by Vietnamese director Tran Anh Hung, must count among the year's most erotic screen images. Not least of them is the opening: a man and woman wake side by side in their Hanoi apartment, stretch like opiated cats, then go about their ablutions and morning t'ai chi exercises to the spacy, languorous cadences of the Velvet Underground's "Pale Blue Eyes". So much sexier and more civilised than Robin Williams bellowing "Good morrrning Vietnam!"

It's hard always to know with Tran Anh Hung where sex ends and sensual mysticism, or plain everyday life, begins. His first film The Scent of Green Papaya seemed to ooze sexual metaphor in its decorously abstract extreme close-ups of fruit and veg. Tran's third film – returning to a miniaturist's contemplativeness after his apocalyptically violent Cyclo – is more directly about sex, and the sexual complexities of family life. The young couple at the start are actually siblings who chastely cohabit, although sister Lien (played by Tran's wife and regular star Tran Nu Yen Khe) is coyly delighted by the incestuous overtones. "We look good together," she beams, "we were made for each other." Certainly they were made for a fashion shoot – two wan beauties swanning around their artily run-down apartment while rain falls in torrents outside (and quite a bit inside too).

Meanwhile, their sister Khanh (Le Khanh) is pregnant by her novelist husband Kien, who seems to spend most of his day distractedly playing with the house grasshopper. The third sister Suong (Nguyen Nhu Quynh) is married to a botanical photographer who has a secret mistress and child stashed away on a secluded island. But Suong herself is having an affair that's cloaked in silence, you might say – she refuses ever to utter a word to her lover.

The elegance of Mark Lee's photography is not just a matter of stylishness but of philosophy – Tran wants objects and moments to resonate with all their potential sensuousness. Yet he walks a thin line between an aesthete's refinement and a delicacy that's almost kitsch. You can get restless visiting a world where every other moment seems to offer an epiphany, and sometimes very little divides a successful image and a misfire: a pair of footprints on a damp wall is powerfully suggestive of a (literally) steamy encounter, while a wet lip mark on a veil draped over a birdcage feels as phonily enigmatic as a red ribbon on a box of Black Magic.

Perhaps the success or failure of particular images is simply subjective, something for viewers to wrangle over among themselves – just as the film's husbands debate the respective visual merits of flowers and faces, an aesthetic seminar which Tran really seems to be holding with himself. The heady intensity of the visuals, however, means that you're sometimes so enraptured that you forget to follow the story, which is elliptical at best. In fact, the family don't seem to know each other, or understand their own story, any better than we know them: the sisters spend much time pondering the insoluble question of a secret love in their dead mother's past. By the end, we barely seem to know the actor brother Hai, who contrives to slip through the narrative like water, and we wonder whether Lien is really a gently spaced-out romantic ingenue or whether there's something more damaged in her other-worldiness.

In effect, Tran is investigating the problem of knowing people and the world, of seeing beyond the alluring surfaces of objects, faces and bodies. But how those surfaces arrest him: even more than Green Papaya, this film is Tran's love letter to his star Tran Nu Yen Khe, whose wispy, sometimes skittish calm is given as lovingly fetishistic a packaging as any male director ever gave his muse. Her sequences showering or washing her hair are hardly your Hollywood idea of bathroom eroticism, more like a hyper-refined phenomenology of flesh and water (even so, just imagine what dream L'Oréal ads Tran could direct).

It's hard to tell whether the film conveys a remotely realistic vision of modern Vietnam. Tran, who grew up in France, shot the film in Vietnam, but The Scent of Green Papaya reconstructed Saigon Fifties in a Paris studio, and there's always a sense in his films of a country imagined from the outside. Certainly the sequences where the photographer visits his island mistress suggest something not quite real – too pure for a tourist-postcard vision, but definitely abstract, a dream Vietnam. Similarly Tran imagines female sexuality from the outside, as a collusive and fascinated male eavesdropper: the three sisters, in a decorous huddle over the cooking, turn out to be discussing penises and wondering what one would taste like fried with garlic.

Which just shows, however rarefied the film appears to be, it always boils down to the basics – sex, sweat and the weather. Even so, there's a sense of constant rapture and an enigmatic open-endedness that make you want to see the film again – I'm about ready for my third viewing. Make sure you see it in the cinema, too – some of the images are so subtly shot, like those footprints on the wall, they barely even register on video.

j.romney@independent.co.uk